Wildfire smoke linked to vocal changes in wild Bornean orangutans

Summary

Tropical peatlands are the sites of Earth’s largest fire events, with outsized contributions to greenhouse gases, toxic smoke, and haze rich with particulate matter. The human health risks from wildfire smoke are well known, but its effects on wildlife inhabiting these ecosystems are poorly understood. In 2015, peatland fires on Borneo created a thick haze of smoke that blanketed the region. We studied its effects on the long call vocalizations of four adult male Bornean orangutans ( Pongo pygmaeus wurmbii) in a peat swamp forest. During the period of heavy smoke, orangutans called less often and showed reduced vocal quality—lower pitch, increased harshness and perturbations, and more nonlinear phenomena—similar to changes in human smokers. Most of these changes persisted for two months after the smoke had cleared and likely signal changes in health. Our work contributes valuable information to support non-invasive acoustic monitoring of this Critically Endangered primate.

Graphical abstract

Highlights

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  Indonesia’s 2015 peatland fires caused the worst sustained air quality ever recorded

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  During and after the fires, orangutans called less and showed reduced vocal quality

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  Orangutans’ vocal changes likely signal illness or other shifts in their health

Abstract

Wildlife behavior; Biological sciences; Zoology